Vacuum holder



Aug. 15, 1967 .1. M. COCITO 3,335,994

VACUUM HOLDER Filed April 27, 1965 Fig.6

INVENTOR JOE MICHAEL COCITO ATTORNEYS United States Patent 3,335,994VACUUM HOLDER Joe Michael Cocito, 11008 Nicholas Drive, Wheaten, Md.20902 Filed Apr. 27, 1965, Ser. No. 451,212 14 Claims. (Cl. 248-363)This invention relates to vacuum holders for thin sheets or films of thetype having a large number of suction holes distributed over the surfaceof a supporting plate, and more particularly relates to improvedstructure for filtering, controllingand distributing the flow of airinto the plural vacuum holes, and for back-lighting sheets of materialsupported by the vacuum holder while photographing them.

It is a principal object of this invention to provide a holder of theabove type in which novel and improved automatic valve means areprovided at each suction hole to virtually close the bore extending fromthe front face of the plate into a vacuum manifold located behind theplate whenever no film or sheet overlies and closes the bore, and saidvalve means automatically opening when a film is laid thereover.

It is another principal object of the invention to provide a holder ofthe above type having a novel foraminous covering over the front face ofthe supporting plate wherein the pores or openings through the coveringare small enough to effectively filter dust out of the air entering thesuction holes to protect the automatic valve means from contamination.

Another major object of this invention is to provide novel. barriers byfilling the pores in the foraminous covering along rows and columns inthe pattern of a grid of rectangular coordinates to isolate each holefrom its neighboring holes to prevent one hole from drawing air from azone which should be under the control of an adjacent hole.

I am aware that there are a number of prior-art patents showingstructures which operate in this same general way, for instance Patents2,910,265, 2,753,181, 2,782,574, 2,594,337, 2,425,921 and 2,198,765, butthe present structure is an improvement from the point of view ofefliciency and economy of manufacture, and from the point of view ofbeing less subject to dust clogging. One of the most serious problemsencountered in connection with valved vacuum-board structures resultsfrom their tendency to collect dust in the bores of the suction holeswith the result that the valves become jammed or the bores clogged, orboth.

This invention teaches simplified valve means which by virtue ofimproved structure have less tendency to become jammed. The presentvalve means takes the form of a ball which is a loose fit in a largerhemispherical bore having an offset smaller bore through its inner endand communicating with a vacuum manifold therebehind. The parts of thevalve means are shaped so that when the vacuum pulls the ball againstthe hemispherical blind end of-the larger bore, the ball cannot possiblyseat tightly enough to fully block the smaller bore, thereby leaving asmall leakage space. This structure provides the desired valving action,without however, completely closing the bore to the flow of air. Suchleakage assures that when the outer end of the larger bore is closed bya film laid thereover, the air within the larger bore and between theball and the film will leak into the manifold by passing through theimperfect seat where the ball attempts to close the smaller bore andthus release the air pressure holding the ball thereagainst to fullyopen the valve. The smaller bore is so located through the blindhemispherical end of the larger bore that the vacuum holder can be sup-3,335,994 Patented Aug. 15, 1967 ported at any angle within a largerange of angles, exceeding and the valve ball will still operateproperly to virtually close the smaller bore when the vacuum pulls theball thereagainst or to roll away from the smaller bore under theinfluence of gravity when the vacuum is released so as to provide alarger and unrestricted opening sufficient to freely pass any collecteddust or lint into the manifold.

The present disclosure shows the improved valve means coupled with anadvantageous manifold structure located behind the pattern of suctionholes and communicating with the bores therethrough. The presentstructure comprises a continuous manifold including a lengthy channelwhich is folded in a serpentine manner and communicates with all of thesuction points sequentially. A vacuum is drawn upon the channel at oneend, and the channel is of such small cross-sectional area that when thesystem is first turned on, the evacuating effort will be appliedinitially to a relatively few valve means near the beginning of theserpentine channel. When these valve means have closed, the vacuumgradient will move along the channel causing each valve means which itapproaches to close in a sequential manner. Therefore, the vacuum pumpneed not be capable of closing substantially all of the ball valvessimultaneously, but rather the pump need be capable only of closing afew of the valve means at any one time.

Another object of this invention is to provide a rela tively simple andeasily machined structure which can be economically manufactured usinginexpensive materials. In one illustrated embodiment the balls are heldin the larger bores by press-fit washer means located in recesses at thefilm supporting end of the bores. These washers may be knurled orotherwise roughened on their outer surfaces so that when a film is laidover the washer, the vacuum from the air hole therethrough can spreadoutwardly through the grooves provided in the front face of the washersby the surface knurling, but these grooves are so small and shallow ascompared with the diameter of the air hole through the washer that inthe event that the film overlies only a portion of the washer includingthe hole therethrough,the holding effect of the vacuum upon the filmwill not be lost by escape through those knurled areas of the washerwhich are not covered by the film. The air hole through the washer canbe placed olfcenter to cause the air to swirl in the larger bore toimprove the cleaning action tending to flush out dust particles.

Another major object of this invention is to provide a foraminouscovering having the capability of glowing under the stimulation of anexternal source of energy. For example, the covering can be atight-woven cloth of fibers or wires coated or impregnated with afluorescent material which glows when stimulated by an ultraviolet lamp.Another possible embodiment would include an electroluminescentcovering, caused to glow by the application of a voltage across spacedlocations of the foraminous covering, which may be made up of laminatedperforate sheets including electroluminescent materials. In this way,the foraminous covering itself can be made to serve as the source oflight to illuminate the sheet or film which is being supported by thevacuum holder.

Other objects and advantages of the present invention will becomeapparent during the following discussion of the drawings, wherein:

' FIG. 1 is a broken elevation view of a vacuum film holder according tothe present invention connected with an external vacuum pump andilluminated by an energy source to cause fluorescence of the frontcovering, a por tion of the front of the holder being cut away to showthe air-hole plate and the manifold construction therebehind;

FIG. 2 is an enlarged sectional view taken along line 22 of FIG. 1, thisfigure showing the upper ball valve in open position and the lower ballvalve in closed position;

FIG. 3 is a sectional view similar to FIG. 2 and showing the same valvestructure lying down in a horizontal position with the left ball valvein open position and the right ball valve in closed position;

FIG. 4 is an enlarged view of the air-hole plate and rear cover plateand showing in detail a preferred structure for the larger and thesmaller bores meeting at a hemispherical surface;

FIG. 5 is a view looking into the larger bore and showing a preferredlocation of the smaller bore; and

FIG. 6 is a view similar to the upper half of FIG. 2, but showingmodified means for holding the ball in the larger bore.

Referring now to the drawings, FIGURES 1 through 5 show preferredembodiments of the invention which include front and rear panel members.The front panel member 1 has a large number of holes arranged in aclosely proximate pattern, and passing all the way through it. Each ofthe holes comprises a larger bore 2 meeting a smaller bore 3 at ahemispherical blind end surface 4, these bores extending from the frontsurface 1a of the panel 1 through the rear surface 11) thereof.

The rear surface has a series of serpentine channels 5 therein which areseparated by ribs 1c and which form a continuous passage commencing inthe center of FIG. 1 and winding around the figure and eventuallyopening into an evacuation outlet 5a which connects to a suitable vacuumpump P through a suitable conduit C. The rear surfaces of the ribs 10mate with a rear closure panel member 10, and the front and rear panelsare held together by any suitable means such as screws 10a as shown inFIGS. 2, 3, and 5.

The manner in which the present board is intended to operate isbasically similar to the functioning of numerous other vacuum holderssuch as the ones illustrated in the patents mentioned above in whichvalve means are provided to automatically close any of the bores whichhave not been covered by film sheets F or other relatively non-porouswebs overlying the front face 1a of the panel 1. In the presentdisclosure the valve means by which the closing of the uncovered boresis accomplished includes a ball 6, located in each of the larger bores 2and fitting it loosely to provide some clearance. The ball 6 is kept inthe bore 2 by a foraminous covering 8, or in FIG. 6,

by a retainer washer 7 having a hole 7a therethrough and having aknurled front face 7b. This washer is a press-fit in a bore 11b in thefront face 11a of a panel 11, having bores 12 and 13 corresponding withbores 2 and 3 in FIG. 2. The roughening of the front face at 7b isunnecessary'if the washer 7 and front face 11a are then covered by aforaminous sheet 8, as will be more fully described below. However theball 6 is retained in the bore 2, it tends to roll away from the mouthof the smaller bore 3 under the influence of gravity, since theintersection of the two bores 2 and 3 is part-way up the hemisphericalsurface 4, or 14, regardless of whether the panel 1 is upright as shownin FIG. 2 or horizontal as shown in FIG. 3. There are a large number ofother angles at which the panel 1 can be disposed relative to horizontaland still have the ball tend to roll away from and uncover the bore 3.

- However, the ball 6 can never seat perfectly against the opening 3a inthe hemispherical surface 4, or 14, where the bore 3 enters the bore 2,because this opening 3a, FIG. 5, is egg-shaped due to the fact that theaxis A, FIG. 5, of the hole 3 does not pass through the center point Kof the hemisphere 4. In the practical embodiment of the invention theballs 6 are steel and in diameter. The bore 2 is A inch in diameter andthe bore 3 is inch in diameter. Its axis A makes an angle 0 of 2.2degrees with respect to the axis H of the bore 2. The pump P comprisesan ordinary domestic vacuum cleaner which provides enough suction toattract the balls 6 to cover the openings of the bores 3 at 3a, but theballs can seat only imperfectly at the egg-shaped openings 3a. When avacuum is drawn upon the bore 2 through the manifold 5 and the bore 3,the ball 6 moves toward the latter and tries to seat against the opening3a at the inner end of the bore 2, as shown at the lower position inFIG. 2. However, when a film F covers and closes the outer end of thebore 2, the air between the ball 6 and the film F bleeds off through theimperfect seating at 3a and thus releases the ball to fall away from theopening 3a under the influence of gravity, except for the case where thebore is at an angle where the opening 3a is at the bottom of the bore 2.The holder is still operative in this position, but its automatic dustflushing action is impaired by failure of the balls to roll around inthe bores 2 as the vacuum is turned on and off, or as the front face ofthe holder is covered or uncovered by films F. If the opening 3a-isoffset from both the vertical and the horizontal axes of the vacuumholder in the position shown in FIG. 5, the ball 6 will probably neverlie directly on the opening 3a due solely to the influence of gravitythereon during normal use of the vacuum holder.

For the purpose of increasing the area of influence of each hole 2, aforairninous covering 8 is secured by cementing or bonding in somesuitable way to the front face 1a of the panel 1. This covering is thendivided into noncommunicating square zones Z by filling spaced rows andcolumns of its pores with a suitable plastic material 9 which can besqueezed into the pores from a nozzle (not shown). The pores in thecovering 8 are so small that the vacuum within any zone Z will tend notto become dissipated even if the film F only partly covers the zone.This is of course a matter of degree, but the film tends to be attractedagainst the covering in a zone provided the film covers most of the areaof the bore 2 lying within that zone.

The forarninous covering 8 can be woven mesh such as metal or plasticscreening, and where the fluorescent effect is desired, a very tightweave, such as a Dutch weave, is especially useful since none of theholes or pores extends straight through the covering 8, but air can passtherethrough only via circuitous routes. As a result, if the wires orplastic filaments are provided with fluorescent properties or coatingswhich glow when excited by the ultraviolet light L, the whole surface ofthe vacuum holder will glow with a substantially homogeneous lightdistribution. It is also desirable to add fluorescent materials to thecement or plastic substance 9 forming the partitions between zones Z ofthe covering 8.

Operation The reasons for the novel structures of the present disclosurewill become apparent during the following explanation of operation. Asis recognized in the prior art, if unlimited vacuum pump facilities areavailable, it is not necessary to virtually close the exposed bore holesthrough the front panel member in locations not overlapped by the filmF, but since it is desirable to use only a relatively small vacuum pumpP in a practical installation, the closure valves shown in the boresbecome necessary in order to conserve the vacuum, especially when only asmall proportion of the bores 2 through the front panel member arecovered by a film -F.

In practical working embodiments of the present invention, the channels5 are milled into or built up upon one of the panel members 1 or 10 onlyto a depth of about A; inch, and the width of each channel is about fiveinches. Since the channels are of relatively small cross-sectional area,they exhibit considerable impedance to the flow of air therethrough withthe result that when the vacuum pump -P is first started, the end of thechannel nearest the conduit C drops in pressure considerably ahead ofthe time that the pressure begins dropping in the more reto firstevacuate the entire manifold to do so. Hence, when the pump P isstarted, the valves close first in the outer channels, andthensuccessively close in a sequence winding around the panels andapproaching the center of the panel members.

Referring now to FIGS. 2', 3, and 6, these figures illustrate novelvalve structures having very practical features. Experience has shownthat the presence of dust in most valve structures is highly damaging totheir operation, and eventually renders the device inoperative. A majoradvantage of the present structure is that the valve has only one movingpart, a smooth ball, which does not tend to entrap or hold dust. Theball 6 has considerable clearance with respect to the bore 2, there-byencouraging air jetting past the ball to flush out the clearance space.However, when the ball is in closed position as shown in the lower halfof FIG. 2, the air which seeks to pass leftwardly through the suctionhole is further restricted by the smallness of the gap between the ball6 and the egg-shaped opening 3a through which the escaping air musttravel to reach the manifold 5. On the other hand when the vacuum isreleased and the ball rolls to the right to a more open position, thedust can easily escape through the bore 3 or 13, which is then openedWider. The escape tends to occur on a subsequent cycle of the valvingaction, the dust being swept along by the air jetting through theclearance between the ball and the end of the bore 3 as the ball issucked up toward the hemispherical end 4. This structure thereforeprovides a small leaky seal when the valve is in closed position, but amuch larger opening when the valve is in open position.

The outer surface 7b of each of the washers 7 of the FIG. 5 embodimentis knurled so that minute grooves will be provided on the outer surfaceof each washer 7 permitting a vacuum to be drawn on the film F over asmuch of the surface area of the washer 7 as is covered thereby, and notmerely over the relatively small area of the hole 711. Some prior artpatents have shown other types of roughening of the outer surface in thevicinity of each suction hole, but many of these structures requireexpensive concentric-groove machining of the front plate itself. Thepresent invention is believed to constitute an improvement by requiringonly inexpensive knurling of the washers themselves before they areinstalled in the bores 11b of the front panel, and where no foraminouscovering is placed over the washers 7.

The present invention is not to be limited to the exact form shown inthe drawings, for obviously changes may be made therein. For example,the shapes of the bores 2 and the valving members 6 can be varied totake cylindrical, or conical forms, and the desired imperfect valvingaction can be obtained by drilling the smaller bore 3 so that itsopening into the bore 2 is a shape which cannot be perfectly sealed bythe selected moving valving member. These and other modifications fallwithin the scope of the following claims.

I claim:

1. A vacuum holder for supporting sheets in a plane, comprising:

(a) a panel member having plural suction holes therethrough, eachincluding a larger bore having a first axis and extending from the frontface of said member thereinto toward the rear and ending at an innersurface, and including a smaller bore having a second axis and extendingfrom the rear of the panel member through said inner surface at alocation spaced from the side wall of the larger bore;

(b) vacuum manifold means on the rear of the panel member andcommunicating with said bores;

(c) vacuum-operated valve means in each larger bore and shaped to rollabout its center therein and to overlie and restrict the entrance to thesmaller bore at the .6 inner surface when sucked therea'gainst by themanifold means, the axis of the smaller bore being skewed with respectto that of the larger bore and with respect to the center of the valvemeans to form an entrance of distorted shape against which the valvemeans can seat only imperfectly; and

((1) means near the front-face for retaining the valve means in thebores.

2. In a holder as set forth in claim 1, said retaining means comprisinga sheet of fibrous cloth secured to said front face of the panel member.

3. In a holder as set forth in claim 2, said material includingfluorescent material; and means for exciting said fluorescent materialto glow.

4. A vacuum holder for supporting sheets in a plane, comprising:

(a) a panel member having plural suction holes therethrough, eachincluding a larger bore extending from the front face of said memberthereinto toward the rear and ending at a hemispherical surface, andincluding a smaller bore offset from the center of the larger bore andextending from the rear of the panel member through said hemisphericalsurface;

(b) vacuum manifold means on the rear of the panel member andcommunicating with said bores;

(c) vacuum-operated valve means in each suction hole and comprising aball of diameter smaller than the diameter of the hemispherical surfacebut larger than the diameter of said smaller bore;

((1) the smaller bore having an axis disposed to exclude the center ofsaid hemispherical surface; and

(e) means near the front-face for retaining the valve means in thebores.

5. In a holder as set forth in claim 4, said retaining means comprisinga sheet of fibrous cloth secured to said front face of the panel member.

6. In a holder as set forth in claim 5, said material includingfluorescent material; and means for exciting said fluorescent materialto glow.

7. In a holder as set forth in claim 4, said larger bore having anenlargement where it meets the front face of the panel member, and saidretaining means comprising a washer pressed into said enlargement andhaving a hole therethrough offset from the center of said larger boreand disposed to pass air toward said hemispheric-a1 surface.

8. In a holder as set forth in claim 4, said smaller bore intersectingsaid hemispherical surface within one quadrant thereof and offset fromplanes passing through its center point parallel to the edges of theholder panel and normal to its front face.

9. In a holder as set forth in claim 4, the axis of the smaller boremaking an acute angle with the axis of the larger bore and crossing thelatter in the plane of the front face of the panel member.

10. In a holder as set forth in claim 4, said smaller bore intersectingthe hemispherical surface in a non-planar peripheral contour againstwhich said ball cannot be perfectly seated.

11. A vacuum holder for supporting sheets in a plane, comprising:

(a) a panel member having plural suction holes ex tending therethrough;

(b) vacuum manifold means on the rear of the panel member andcommunicating with said suction holes;

(c) a porous covering over the front of the panel member and secured tothe surface thereof between suction holes, the size of the pores in thecovering being very small as compared with the size of a suction hole;and

(d) sealing means filling the pores in narrow strips disposed betweenadjacent suction holes to divide the covering into adjacentnon-communicating zones each surrounding a suction hole and of greaterarea than the area of a hole.

12. In a holder as set forth in claim 11, said covering comprising awoven cloth.

13. In a holder as set forth in claim 11, said covering comprising acloth woven of filaments including fluorescent material.

14. In a holder as set forth in claim 11, said covering comprising afor-aminous web including fluorescent material; and means for excitingsaid fluorescent material to glow.

References Cited UNITED STATES PATENTS ROY D. FRAZIER, Primary Examiner.

I F. FOSS, Assistant Examiner.

1. A VACUUM HOLDER FOR SUPPORTING SHEETS IN A PLANE, COMPRISING: (A) APANEL MEMBER HAVING A PLURAL SUCTION HOLES THERETHROUGH, EACH INCLUDINGA LARGER BORE HAVING A FIRST AXIS AND EXTENDING FROM THE FRONT FACE OFSAID MEMBER THEREINTO TOWARD THE REAR AND ENDING AT AN INNER SURFACE,AND INCLUDING A SMALLER BORE HAVING A SECOND AXIS AND EXTENDING FROM THEREAR OF THE PANEL MEMBER THROUGH SAID INNER SURFACE AT A LOCATION SPACEDFROM THE SIDE WALL OF THE LARGER BORE; (B) VACUUM MANIFOLD MEANS ON THEREAR OF THE PANEL MEMBER AND COMMUNICATING WITH SAID BORES; (C)VACUUM-OPERATED VALVE MEANS IN EACH LARGER BORE AND SHAPED TO ROLL ABOUTITS CENTER THEREIN AND TO OVERLIE AND RESTRICT THE ENTRANCE TO THESMALLER BORE AT THE INNER SURFACE WHEN SUCKED THEREAGAINST BY THEMANIFOLD MEANS, THE AXIS OF THE SMALLER BORE BEING SKEWED WITH RESPECTTO THAT OF THE LARGER BORE AND WITH RESPECT TO THE CENTER OF THE VALVEMEANS TO FORM AN ENTRANCE OF DISTORTED SHAPE AGAINST WHICH THE VALVEMEANS CAN SEAT ONLY IMPERFECTLY; AND (D) MEANS NEAR THE FRONT-FACE FORRETAINING THE VALVE MEANS IN THE BORES.